Agrocybe cylindracea bio-residues: a sustainable source of ergosterol-rich bioactive extracts

The world production of edible mushrooms has increased more than 30‐fold since 1978 and, on average, each customer consumes 5 kg of mushrooms per year [1]. Depending on the dimension of the mushroom industry, the amount of obtained by-products may range from 20 to 35% in weight of fresh mushroom [2]. Indeed, 38% of the 90 million tonnes of food waste produced by the European Union every year has its origin in the food manufacturing sector [3]. However, there are several strategies of transforming these wastes into high value-added products based on the cascade use principle, and this is exactly what the MicoBioExtract project aims to perform. Thus, the bio-residues of a popular edible mushroom in southern Europe, Agrocybe cylindracea, were studied as a sustainable source of bioactive extracts [4]. Ergosterol has been reported to be one of the most important compounds, contributing to the health-promoting benefits, associated with mushrooms’ consumption [2]. Its extraction was performed using a heat-assisted technique and applying the response surface methodology, in order to optimize the combined effects of the variables time, temperature and solvent percentage, using a circumscribed central composite design with 16 independent combinations and 4 replicated centre points. At the optimum condition predicted by the model, the bioactivity of the extract was tested, evaluating the antioxidant (TBARS assay) and cytotoxic (in a porcine liver primary cell culture, PLP2) activities. The results obtained from the optimization study showed a significant interaction between temperature and extraction time, with an 8.24% extraction yield. The global optimum condition for ergosterol extraction predicted by the model was 150 min at 90 °C, with 329 mg of ergosterol per 100 g of dry weight sample. Regarding the bioactive potential, namely the antioxidant activity, this extract was capable of preventing the formation of malondialdehyde, a secondary product of lipid peroxidation in the TBARS assay. Concerning the cytotoxicity of the extracts against the PLP2 cell line, the results showed no significant cytotoxic effect, with GI50 values higher than 400 μg/mL. Thus, the extraction of molecules with a high nutritional and bioactive value from mushroom bio-residues and the goal to incorporate them in functional foods and nutraceuticals could boost the circular bio-economy, and help developing strategies towards promoting sustainability.The authors are grateful to FCT, Portugal and FEDER under Programme PT2020 for financial support to CIMO (UID/AGR/00690/2019) and the research contracts of J. Pinela (Project AllNatt, POCI-01-0145-FEDER-030463) and L. Barros; this work was funded by FEDER through POCI, within the scope of project MicoBioExtract (POCI-01-0247-FEDER- 033939).